METHODS AND RESULTS:

CD117+ cells were isolated from the bone marrow mononuclear cells of GFP-transgenic or normal C57/BL6 mice. The myogenic differentiation of CD117+ cells was achieved by cultivation with TGF-beta. Using an acute myocardial infarction model, we also tried to regenerate infarcted myocardium by implanting untreated (newly isolated) or preprogrammed (24 hours of cultivation with 5 ng/mL TGF-beta1) CD117+ cells intramyocardially. TGF-beta increased the cellular expression of myosin, troponins, connexin-43, GATA-4, and NKx-2.5, which suggested that it induced the myogenic differentiation of CD117+ cells. Compared with the effects of PBS injection only, the microvessel density in the infarcted myocardium was increased significantly 3 months after the implantation of either TGF-beta-preprogrammed or untreated CD117+ cells. Moreover, many of the TGF-beta-preprogrammed CD117+ cells were stained positively for myosin, whereas few of the untreated CD117+ cells were. Histological analysis revealed newly regenerated myocardium in the left ventricular anterior wall after the implantation of TGF-beta-preprogrammed cells but not untreated cells. Furthermore, the left ventricular percent fraction shortening was significantly higher after the implantation of TGF-beta-preprogrammed cells than after the implantation of untreated CD117+ cells.